This invention relates to seal arrangements and in particular seals useful in subterranean recovery of oil and gas. More particularly, it relates to a mechanical seal for inserts in drill pipe sections used in such recovery.
One particular illustration of sealing arrangements includes measurement while drilling applications. In such applications, highly sophisticated and sensitive electronic and mechanical apparatus are placed downhole to sense the parameters of the surrounding formation and the drill string, to analyze and convert the collected information and to record and transmit the information to the surface of the earth. The electronic apparatus is typically contained in an insert cover which is positioned in the interior of the drill string which is lowered into the borehole through the earth formations.
The interior of the drill string and in particular the interior conduit of the pipe sections for holding the insert is machined to close tolerances for mating with the insert cover. A variety of seal arrangements have been devised to seal inserts in the drill pipe. Typically, a seal arrangement requires a close tolerance between mating parts with a deformable seal positioned between the machined parts. One form of the deformable seal is an O-ring. Typically, for an O-ring having deformation characteristics of 90 durometers to maintain a pressure seal of 3000 psi, a tolerance between the insert cover and the interior of the drill pipe sections must be less than 0.006 in. This degree of tolerance is difficult to achieve with long internal boring machines.
Furthermore, with use the insert must be removed and replaced numerous times. This use will result in deterioration of the tolerance by scratching, bending, expansion, etc. Further as the measurement while drilling apparatus is used in deeper formations, the pressure differential between the exterior and interior of the insert increases to a point where additional sealing arrangements are necessary beyond the mating of the insert cover and O-ring with the interior of the drill string.
In oil recovery enhancement techniques, and in wells used in geothermal production, these pressure seals frequently must function under conditions of elevated temperature, high pressures and corrosive surface environment. The O-ring type seals used under high pressure differential will fail unless the tolerance between the mating parts is increased. Because of the harsh environment and other technical requirements associated with such applications, a very durable seal arrangement that can be utilized with commercial drill stems is necessary.
In accordance with the invention, there is provided a seal arrangement that includes a tubular body member having a longitudinal passage therethrough. Along the passage there is an annular recess in which an insert cover in its entirety is disposed. Along the peripheral edge of the insert, a deformable edge is formed to mate with the interior of the annular recess. The interior of insert cover, that is the space between the insert cover and the body member is of a relatively lower pressure than that of the exterior of the insert in the longitudinal passage. Between the deformable edge and the interior of the annular recess is situated deformable spacer material.
The seal is positioned toward the portion of the edge away from the insert. Application of hydraulic pressure on the inner surface of the peripheral edge causes a radially outward bending expansion and elastic and/or plastic deformation of the edge and forces the outer surface of the edge into a sealing engagement with the deformable spacer material and in turn that into a sealing engagement with the opposed surface of the interior of the annular recess in which the insert cover is disposed.